1. Field of the Invention
The present invention relates to a photographic material and a method of forming images using the same. More particularly, the present invention relates to a novel photographic material in which titanium dioxide is used as a light-sensitive component and a copper (II) salt is used as an image-forming material, and to a method of forming images using the same.
2. Description of the Prior Art
Silver halide photographic processes and silver halide diffusion transfer processes have been widely used as high speed photographic processes. Known fairly high speed photographic processes include photographic processes for obtaining images by thermal development using a long-chained fatty acid as an image-forming material ("Dry Silver", trade name, produced by Minnesota Mining and Manufacturing Co.) as disclosed, for example, in U.S. Pat. Nos. 3,152,903, 3,152,904 and 3,457,075, photographic processes for obtaining silver images by silver ion physical development using titanium dioxide as a light-sensitive component (the "RS Process" of Itek Co.) as described, for example, in G. L. Mcleod, Photographic Science and Engineering, 13 93 (1969) and E. Berman, ibid., 13 50 (1969), photographic processes for obtaining silver images by silver ion physical development using a diazonium compound as a light-sensitive component ("PD Process" of the Philips Co.) as described, for example, in H. Jonker et al., Photographic Science and Engineering, 13 1 (1969); ibid., 13 33 (1969); ibid., 13 38 (1969); ibid., 13 45 (1969); and J. Photographic Science, 19 96 (1971), and the like. Each of these photographic processes has their own characteristic features as to sensitivity, image quality, rapid processing, dry processing, shelf life, resolving power, or the like. However, they generally require the use of large amounts of silver since silver compounds are employed therein as a light-sensitive or image-forming material (or, in the case of silver halide color photographic processes, as an intermediate medium for forming color images). This not only makes them expensive since recovery and reuse of silver are practiced only in some of them on account of facilities, etc., but can be a fatal disadvantage in them since there is a fear that silver resources may become exhausted.
Therefore, development of a photographic process using silver in a reduced amount or a photographic process not using silver, i.e., so-called non-silver photographic process is desired. Although many non-silver photographic processes are known and they are too numerous to enumerate here, they are generally inferior in sensitivity to photographic processes using silver. Known photographic processes for producing images of non-silver metals using as a light-sensitive component or development nucleus-forming material a small amount of silver compounds or non-silver compounds include physical development processes employing non-silver metal ions, such as those described, for example, in U.S. Pat. Nos. 3,512,972, 3,893,857, 2,609,295, 2,733,144, 2,738,272, 2,750,292, 2,763,484 and 3,775,773; H. Jonker et al.,
Photographic Science and Engineering, Vol. 13, p. 1 (1969); ibid., Vol. 13, p. 33 (1969); ibid., Vol. 13, p. 38 (1969); ibid., Vol. 13, p. 45 (1969); and H. Jonker et al., Journal of Photographic Science, Vol. 19, p. 96 (1971). In these non-silver metal physical development processes, the processing steps involve amplification of images to a considerable extent so that images and formed at fairly high sensitivities, but they suffer from such disadvantages that reducible metal ions, which are the image-forming material, generally tend to be reduced by reducing agents present simultaneously in developing solutions, fog tends to be generated on the images, the loss of metal ions is not limited to small quantities thereof, and waste developing solutions tend to cause deleterious environmental pollution problems since they contain ions of heavy metals.
It has long been known that photoconductive (or semiconductive) materials, such as titanium dioxide, etc., when exposed to actinic light, are capable of reducing various kinds of materials having strong oxidative properties, such as metal ions (e.g., silver salts), to reduced forms thereof, and photographic processes applying the phenomenon have been proposed, for example, in U.S. Pat. Nos. 3,700,447, 3,414,410, 3,390,989, 3,424,582, 3,512,972, 3,711,282, 3,380,823, 3,623,865, 3,547,635, 3,713,823, 3,674,489, 3,893,857 and 3,706,560; G. L. McLeod, Photographic Science and Engineering, Vol. 13, P. 93 (1969); E. Berman, ibid., Vol. 13, p. 50 (1969) and E. J. Delorenzo et al., ibid., Vol. 13, p. 95 (1969). Of these processes, the one employing silver physical development has been put to practical use as the "RS Process" described hereinbefore.
These photograhic processes, however, also unavoidably suffer from the above-described defects in stability of the physical development solutions, fogging, loss of metal ions, pollution problems caused by waste developing solutions, etc., since in these processes images are formed by immersing the light-sensitive layer containing a photoconductive material into a so-called physical development solution containing both ions of a metal (such as silver, copper, tin, etc.), which is the image-forming material, and a reducing agent (or by successively immersing the light-sensitive layer into a solution of a metal ion and then into a solution of a reducing agent) after imagewise exposure thereof.
Photographic materials having a light-sensitive layer containing an oxidizing agent such as a metal ion, etc., in combination with a photoconductive material, and image-forming processes using the same have also been proposed. U.S. Pat. No. 3,052,541 and Japanese Patent Applications (OPI) 122,325/74 and 18,531/76 disclose photographic materials containing a silver salt and a photoconductive material. U.S. Pat. Nos. 3,718,465, 3,661,587 and 3,152,903 disclose, as examples of oxidizing agents to be incorporated into light-sensitive layers in combination with a photoconductive material, non-silver metal salts such as copper salts, as well as silver salts. However, silver salts are chiefly employed therein. These photographic materials containing metal ions are capable of forming images of metals generated by the reduction of the metal ions (so-called print out images) directly by exposure or by a modified processing.
These photographic materials, which contain simultaneously a photoconductive material and an oxidizing agent, such as metal ions, have to be subjected to a fixing since they generally form print out images directly by exposure, and can hardly be a high speed photographic material because, in general, no amplification step is involved therein.